The present invention relates to Venturi tubes in general, and more particularly to a Venturi tube which is particularly suited for the differential pressure measurement in flowing gas/particulate material media with high dust loading at temperatures in excess of 100.degree. C. and at elevated pressures.
During the performance of pressure measurements and differential pressure measurements in conduits or containers through which gases with high dust loading flow of through which a finely granular to pulverulent particulate material is pneumatically conveyed by a carrier gas, problems are encountered time and time again. Herein, the encountered disturbances are predominantly attributable to the deposition of dust on the measuring surfaces of the measuring apparatus being used, in the pressure measuring chambers themselves, or in the pulse conduits between the dust-conveying conduit and the pressure measuring apparatus. As a result of the deposition of dust in the pulse conduits, the measuring apparatus can be often put out of operation after only a short period of use.
A measurement problem of the above kind, during which the aforementioned difficulties can occur, comes into existence in practical application for instance during the measurement and supervision of the mass flow of a finely granular to pulverulent solid fuel which is pneumatically conveyed by means of a carrier gas from a storage bin to a gasification arrangement or plant in which the solid fuel is gasified by partial oxidation with oxygen. In this context, it is desired that the proportion of the carrier gas needed for the pneumatic conveyance be as low as possible. So, for instance, according to a method described in U.S. Pat. application Ser. No. 571,518, the fuel/gas mass flow which is supplied through a pneumatic conduit to the gasification plant is measured and supervised with the aid of a radiometric density measurement as well as a differential pressure measurement at a Venturi tube while utilizing a process computer. This particular process, like the other known processes of this kind, suffers of the above-mentioned problems.